JP-A-2001-133249 and JP-A-2002-71346 disclose a drive unit and a surface texture measurement instrument. The drive unit moves along the surface of a measurement work, and includes a detector that measures the surface roughness, the surface rising and falling, the contour, or other features of the measurement work.
The drive unit of JP-A-2001-133249 is configured to include: a guide rail having the cross section of downwardly-oriented substantially-U-shape with two reference surfaces, which are disposed parallel to the movement direction of the detector with an angle of 90 degrees therebetween; a slider also having the cross section of downwardly-oriented substantially-U-shape, being fit to the outside of the guide rail to be able to freely swing, and keeps hold of the detector in the guide rail; and drive device for moving the slider along the guide rail. The drive device is configured to include: a motor; a feed screw axis that is rotated by the motor; and a feed piece screwed to the feed screw axis and coupled to the slider. Therein, the feed screw axis is disposed at the position above the slider to be parallel to the guide rail.
The surface texture measuring instrument of JP-A-2002-71346 is configured to include: a guide; a slider formed to configure a rectangular frame in cross section to include the guide therein, is fit to the outside of the guide to be able to freely slide, and is keeping hold of a detector on the bottom surface; and drive device for moving the slider along the guide rail. The drive device is configured to include: a motor; a ball screw that is rotated by the motor; and a nut screwed to the ball screw and coupled to the slider. Therein, the ball screw is disposed at the position above the slider to be parallel to the guide rail.